Passive and active escapement for sound resonance

ABSTRACT

In pressure-free condition, music is produced automatically by resonance of free matter. In this instance of freedom, sound is produced and propagated. If a finger is softly placed on an excited resonating bell, the sound of the bell stops. In the field of electrical sound reproduction, the sound emitters such as loudspeaker diaphragms, are always excited by the following note and hardly have time to resonate. As opposed to musical instruments which require an escapement, the field of electrical sound reproduction disregards this. The present method aims at creating systematic micro-interruptions of the electric audio signal, thereby providing freedom to the diaphragm and an unhampered sound quality. Said micro-interruptions thus constitute the systematic acoustic artificial escapement of electroacoustic systems. Said micro-interruptions depend on the inertia of the transducer, but must be implemented at speeds of at least two to three times of the sound frequency activity of the transducer or of the acoustic enclosure. An adjustable electronic clock regularly monitors a unipolar or bipolar switch, in the form of an electric contact such as a transistor, which interrupts the electric system powering the enclosure. The diaphragms become actively resonant in normal mode, through the acoustic escapement which is useful to the whole acoustic and audio-visual world. Said escapement decreases the phenomenon of acoustic compression which causes deafness, and is therefore useful for the medical field.

BACKGROUND OF THE INVENTION

All musical instrument acoustic systems have the particular feature ofrequiring to be musically excited through being struck, being activatedby air or being initiated by a bow the strings of which strike cords.This principle in which tension is free to be released after having beencreated by a mechanical stress imposed by the musician, demonstrates howmusic resonates when unrestricted, by free resonance of matteraccomplished by the music itself in a brief instant of relaxation. Inthis situation of unrestriction, the sound emanates and can propagate.If we consider the case of a bell that has been struck and isresonating, if we lightly touch it with the finger, the bell ceases todeliver sound. The sound no longer propagates; it is deadened,imprisoned.

In the field of electrical sound reproduction, sound emitters such asloudspeaker membranes always get excited from the note that follows anddo not have any free time to resonate. Contrary to musical instrumentswhich require an escapement, the sound reproduction field usingelectrical excitation overlooks this fact, although physicallyunavoidable. Electro-acoustic transducers made up by a coil and a magnetestablish an unceasing and continuous constraint on the membrane whichis constantly subject to the pressure from the driving force of theelectrical audio signal and from uncontrolled micro-currents in theamplifiers driving them.

SUMMARY OF THE INVENTION

The method disclosed herein consists in systematically creatingmicro-interruptions of the electrical audio signal giving the membraneits freedom and removing a limitation to sound quality, the membrane nolonger being constrained and becoming available, able to breathe as itwere and take up the space it needs. These micro-interruptions thusprovide an artificial, systematic and acoustic escapement forelectro-acoustic systems. The micro-interruptions depend on the inertiaof the transducer, but should operate at speeds of at least two to threetimes the velocity of the sound frequency of the activity of thetransducer or a loudspeaker.

This is in no way some system for regulating and controlling informationto get a precise signal shape. It simply involves a systematic processthe regular velocity of which is set as a function of the moving mass,and the constraints of transforming electrical energy into mechanicalmotion energy. The duration of interruption is approximately identicalto the duration of activity, but can be half this if weight is low, theescapement, in other words the time during which the membrane isunrestricted without electrical drive, being instantaneous. Thetransducer is disconnected from its drive for a shorter period.

During this passive free phase, at least some resistance of very lowimpedance value is in series with the transducer or loudspeaker, saidimpedance being of the self-inductance or capacitive type, helps theescapement through its back EMF, thereby cancelling more rapidly theactive audio modulation drive giving the membrane escapement its freedomfor a very brief period of around the order of 100,000ths of a second.In effect, if the micro-interruptions are of at least twice the soundfrequency of the transducer, to take for example mid-range frequenciesof 15,000 Hz, the micro-interruption frequency which controls theescapement will be, if we take a figure of three times, 45,000 Hz. Thisescapement time can be half with an impedance, a wound resistance thusaround some 90,000ths of a second or let us say 100,000ths of a second.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Apparatus for carrying out the invention can be constructed by a personskilled in the art, and the example of an embodiment is non-limiting.

The apparatus constitutes an acoustic escapement for the soundreproduction field in which the drive for at least one electro-acoustictransducer or a 35 Hz to 20,000 Hertz active loudspeaker or acousticenclosure is cut off for the duration of a systematic, repetitive andregular duration of a micro-interruption. A controllable electronicclock regularly drives a single- or double-pole switch in the form of anelectrical on-off switch such as a transistor or a solid state switchwhich-shuts off the electrical drive circuit for the loudspeaker at arate of one 80,000th of a second escapement and one 80,000th of a secondactivity. A 0.3 Ohm self-inductance coil is incorporated in series intothe loudspeakers circuit. The self inductance reacts both to the currentbeing switched on and off, and helps the escapement effect and activesound effect, through its induced back EMF, electrically in series withthe loudspeaker coil or coils.

An apparatus and a method are provided for artificial acousticescapement for sound reproduction allowing acoustic sonority whichpreviously was kept prisoner as a result of constant electric activityto now manifest itself. Loudspeaker membranes become active throughtheir own resonance, thanks to acoustic escapement useful for all areasof the acoustic and audio-visual field. As the escapement decreasesacoustic compression phenomena which are a factor in deafness, theinvention is useful also in the medical field.

1. A method for sound reproduction creating micro-interruptions in anelectrical audio signal driving an electro-acoustic transducer orloudspeaker, said micro-interruptions constituting systematic artificialescapement and being controlled at rates of at least twice that of thefrequency activity of the transducer or loudspeaker, allowing a membranethereof freedom and removing restrictions on spatial sound quality. 2.The method according to claim 1, wherein at least one low resistanceself-inductive or capacitive load is mounted in series with the stillelectrically-coupled acoustic transducer or loudspeaker whereby the backEMF resulting from said load reinforces the escapement effect. 3.Apparatus for sound reproduction comprising a controllable electronicclock regularly driving a solid-state electrical switch or a transistorfor interrupting rhythm of at least twice a frequency rate of the soundactivity thereof, whereby, to take the case of interruptions driven atone 80,000ths of a second corresponding to the escapement and with aperiod of activity identical thereto, restrictions on the sound qualityof the membrane are lifted.
 4. Apparatus according to claim 3, wherein atransducer or loudspeaker is provided with at least one impedance, woundresistance, for reinforcing the escapement activity.
 5. The apparatusaccording to claim 3, for application in the medical field.